Muscle-Specific Basis of OPMD

项目总结 核多聚(A)结合蛋白1(PABPN1)是一种广泛表达的蛋白，在细胞周期调控中发挥重要作用。 转录后基因表达调控的多步骤。短时扩张的聚丙氨酸束 PABPN1的N末端导致眼咽肌营养不良症(OPMD)。患者患有 OPMD有特定肌肉的进行性减弱，最明显的是咽部肌肉。中的缺陷 咽部肌肉功能会导致窒息和反流，导致肺炎或猝死。那里 目前还没有治疗OPMD的方法。关于无处不在的病毒的机制仍有许多未知 这种丙氨酸扩张的PABPN1的表达导致肌肉特异性病理。我们发现， 在小鼠和人的骨骼肌中，PABPN1的mRNA和蛋白的稳定水平都大大降低， 与其他组织相比，尤其是那些受OPMD影响的组织。骨骼肌中PABPN1的低水平表达 可以使这种组织容易受到丙氨酸扩张的PABPN1的有害影响。Pabpn1的低水平 肌肉中存在的转录本表明组织特有的转录或转录调控机制 转录后水平，或者两者兼而有之。我们发现Pabpn1在不同组织中的表达受到部分调控 通过转录后调节转录稳定性的机制，但还需要进一步的研究来充分 阐明PABPN1的表达是如何被控制的。该提案的目标是测试我们的工作假设 骨骼肌中低水平的PABPN1使该组织容易受到丙氨酸扩张的有害影响 PABPN1。为了确定导致PABPN1在肌肉中低水平表达的机制，我们将 绘制调控骨骼肌中Pabpn1转录本稳定性的顺式元件图(AIM 1)并鉴定与PABPN1转录本结合的细胞因子(RNA结合蛋白和miRNAs)以 以组织特异性方式调节转录本的稳定性(目标2)。此外，我们将确定是否 转录机制导致骨骼肌中PABPN1转录本水平较低(目标3)。的 对于OPMD特别重要的是，我们将开发两个新的小鼠模型(都是PABPN1基因敲除小鼠和 一个丙氨酸扩展的PABPN1 Knockin小鼠)，我们已经创建了它来直接测试是否减少了 PABPN1水平加剧了丙氨酸扩张的PABPN1引起的病理(目标4)。长期目标 我们的研究之一是理解为什么突变的PABPN1的普遍表达会导致肌肉特异性 疾病。这些研究意义重大，因为它们将确定可以被操纵的途径，以改善 OPMD患者的生活质量。此外，这些研究可以为以下方面奠定基础 了解其他疾病的组织特异性病理学。

PROJECT SUMMARY The nuclear poly(A) binding protein 1 (PABPN1) is a ubiquitously expressed protein that plays critical roles at multiple steps in post-transcriptional regulation of gene expression. Short expansions of the polyalanine tract in the N-terminus of PABPN1 lead to Oculopharyngeal Muscular Dystrophy (OPMD). Patients who suffer from OPMD have progressive weakening of specific muscles most notably those of the pharynx. Defects in pharyngeal muscle function can cause choking and regurgitation leading to pneumonia or sudden death. There is no current treatment for OPMD. Much is still unknown regarding the mechanism by which ubiquitous expression of this alanine-expanded PABPN1 leads to muscle-specific pathology. We have discovered that the steady-state levels of both PABPN1 mRNA and protein are drastically lower in mouse and human skeletal muscle, particularly those impacted in OPMD, compared to other tissues. The low levels of PABPN1 in skeletal muscle could predispose this tissue to the deleterious effects of alanine-expanded PABPN1. The low level of Pabpn1 transcript present in muscle indicates tissue-specific regulatory mechanisms at either the transcriptional or post-transcriptional level or possibly both. We find that Pabpn1 expression in different tissues is in part regulated by a post-transcriptional mechanism that modulates transcript stability but further studies are needed to fully elucidate how PABPN1 expression is controlled. The goal of this proposal is to test our working hypothesis that low levels of PABPN1 in skeletal muscle predispose this tissue to the deleterious effects of alanine-expanded PABPN1. To define the mechanisms that lead to the low levels of expression of PABPN1 in muscle, we will map the cis-elements responsible for modulating the stability of the Pabpn1 transcript in skeletal muscle (Aim 1) and identify the cellular factors (RNA binding proteins and miRNAs) that bind to the PABPN1 transcript to modulate transcript stability in a tissue-specific manner (Aim 2). In addition, we will determine whether transcriptional mechanisms contribute to the low levels of PABPN1 transcript in skeletal muscle (Aim 3). Of particular importance to OPMD, we will exploit two novel mouse models (both a PABPN1 Knockout mouse and an alanine-expanded PABPN1 Knockin mouse) that we have create to directly test whether a decrease in the level of PABPN1 exacerbates the pathology induced by alanine-expanded PABPN1 (Aim 4). The long-term goal of our studies is to understand why ubiquitous expression of mutant PABPN1 leads to a muscle-specific disease. These studies are significant as they will identify pathways that could be manipulated to improve the quality of life for patients that suffer from OPMD. Furthermore, these studies could lay the groundwork for understanding tissue-specific pathology in other diseases.